High-definition telephoto lens



SEARCH BQQM Jan- 5, 1970 J. M. BALUTEAU ErAL 3,488,107'4 yHIGH-DEFINITION TELEPHOTO LENS Filed Sept. 13, 1967 United States PatentO Int. cl. ozb 9/00 U.S. Cl. 350-214 4 Claims ABSTRACT F THE DISCLOSUREA high-definition telephoto lens comprising two lens groups G1 and G2having six elements respectively. The six elements of the group G1 are,going towards the film, a first bconvex convergent element, a secondbiconcave divergent element, a third bconvex convergent element, afourth biconcave divergent element, a fifth bconvex convergent elementand a sixth divergent element; and the five elements of the group G2are, going towards the film, a seventh plane-concave element, an eighthplane-convex element, a ninth divergent meniscod element, a tenthconvergent meniscod element and an eleventh divergent meniscod element.This telephoto lens, which has a high separating power, is of use moreparticularly for photography from satellites.

The invention relates to a telephoto lens, particularly to ahigh-definition telephoto lens-i.e., a telephoto lens having a highresolving power-of use more particularly but not solely for photographyfrom satellites.

One form of telephoto lens comprises a convergent group of lens elementsand a divergent group of lens elements, separated by a space largeenough for the resulting focal distance to be appreciably greater thanthe total size of the system. A common disadvantage of this feature isthat the divergent group may amplify aberrations of the convergentgroup.

According to the invention, there is provided a telephot-o lens for usein conjunction with an image-receiving surface, consisting of two lensgroups designated G1 and G2, of which the lens group G2 is arranged tobe the nearer one to said surface, the lens groups G1 and G2 having sixand five elements respectively, the six elements of the group G1 being aconvergent group formed by, going towards the image-receiving surface, afirst biconvex convergent element, a second biconcave divergent element,a third bconvex convergent element, a fourth biconcave divergentelement, a fifth bconvex convergent element and a sixth biconcavedivergent element, and the five elements of the group G2 being adivergent group formed by, going towards the image-receiving surface, aseventh plano-concave element, an eighth plano-convex element, a ninthdivergent meniscod element, a tenth convergent meniscod element and aneleventh divergent meniscod element.

The invention will now be described by way of example with reference tothe accompanying drawing, of which the single figure is a diagrammaticview of a telephoto lens n accordance with the invention.

The illustrated telephoto lens comprises two groups of lens elements.Group G1 has a positive resultant focal length F1, that is to say, it isa convergent group, the

maximum and minimum values of the focal length F1 of lens group G1 beingdefined by the double inequality:

where F is the focal length of the complete telephoto lens.

3,488,107 Patented Jan. 6, 19,70

ICC

The second lens group G2 has a negative resultant focal length F2, thatis to say, it is a divergent group, the maximum and minimum values ofthe focal length F2 of lens group G2 being defined by the doubleinequality:

A space d exists between the main image plane of the lens group G1 andthe main object plane of the lens group G2, the maximum and minimumvalues of the space d being defined by the double inequality:

4F 9F 25SdS 25 The group G1 comprises six elements which are, goingtowards an image-receiving surface formed by a film, (not shown), afirst bconvex convergent element L1, a second biconcave divergentelement L2, a third bconvex convergent element L3, a fourth biconcavedivergent element L4, a fifth bconvex convergent element L5 and a sixthbiconcave divergent element L6. The elements L1, L3, L5 have similarindexes n1, and the elements L2, L4, L6 have similar indexes n2. Eachelement group (L1. L2), (L3, L4) and (L5, L6) has a focal lengthsubstantially equal to three times the focal length F1 of the. group G1.

The group G2 comprises five elements which are, going towards the film,a substantially plano-concave element L7 and a substantiallyplano-convex element L8, these two elements possibly being stucktogether -by way of having common curved surfaces, a divergent meniscodelement -L9 of which the concave surface is disposed near the film, aconvergent meniscod element L10 of which the concave surface is disposednear the film, and a divergent meniscod element L11 of which theconcavity is disposed near the film; the elements L10 and L11 possiblybeing stuck together. The elements L7, L8 are made of glasses which arevery similar indexes but different dispersive powers.

A lens of this kind can have an aperture of F /4 and a field of about12.

For good correction of geometric aberrations, the group G1 consists ofthree groups having substantially equal focal lengths. For the samereasons, and in contrast to known formulae for telephoto lenses, thedivergent elements of the group G2 have their concavities facing to therear, .e., towards the film. For good correction of chromaticaberrations, the group G1 is formed by glasses which, taken in pairs,form substantially apochromatic pairsi.e., since the extensions for thelines C and F coincide, the extension at d has the same common value.The elements L7, L8 are devised to cancel the spherical overcorrectioncorresponding to the line F.

In the drawing, the radii of curvatures of the various lens elements aredesignated each by the reference R plus a first index characteristic ofeach element and a second index denoting the order in which the lenselement surface is met going towards the film. Glass thicknesses aredesignated each by the reference E plus the same index as thecorresponding lens element, and the spaces between two consecutive lenselements are designated each by the reference e plus the two indexes ofthe lens elements separated by the particular space concerned.

In a preferred form of the telephoto lens in accordance with theinvention, the radii of curvature of the lens elements meet thefollowing conditions:

For the lens element L1:

0.5F R11 0.6F

For the lens element L3:

For the lens element L5:

0.4F R51 0.5F

For instance, a lens according to the invention having a focal lengthF=402.45, (all dimensions being given in divergent ele'ment, and the veelements of the group G2 being a divergent group formed by, goingtowards the image-receiving surface, a seventh plano-concave element, aneighth plano-convex element, a ninth divergent meniscoid element, atenth convergent meniscoid element and millimetres-mm.) an aperture ofF/4 and covering a 5 an eleventh divergent meniscoid element. 57 x 57mm. format, comprises lens elements having the 2. A telephoto lens asclaimed in claim 1, wherein the following characteristics. rst andsecond elements, the third and fourth elements Its physical lengthoverall is 186.2, and the lens eleand the fifth and sixth elements formthree doublets of ment surface radii of curvature R, glass thicknessesE, substantially the same power. spaces e between lens elements, indicesnld for the length 3. A telephoto lens as claimed in claim 1, whereinthe d, dispersive powers V and useful diameters D of the seventh andeighth elements are stuck together, the indices individual lens elementsare represented by the following of the glasses of which such elementsare made being table: similar and their dispersive powers beingdifferent.

Glass thicknesses Radiioi and lens Length,d Dlsperslve Useful lenscurvature,R spaelngs,dE lndices,nd powers, V dlameters,D

all

R 11= 219 L1..... E1 =10.7 1.61375 55.5 10o 12 =0.11 R 21=272.185 L2 E2=6.0 169604 36.2 100 e23 =0 n 31= 221.1 L3 E3 =10.7 1.61375 55.5 100 e34=0.11 R 41=334.965 L4--... E4 =6.0 1.69664 36.2 100 c45 =0 R 51= 187 L5E5 =10.7 1.61375 555 100 R 52=50o.25s 56 :0.11

E 11=-177.527 L6 E6 =6 1.69664 36.2 100 67 =68.9 R 71= a, L7 E7 :3.21.62375 56.9 5s

:78 =0 (lens elements stuck together) R s1: 77 Ls Es =10.7 1.62025 3625s R 82=l m :69 =0 R 91= 92.94 L9 E9 =4 1.69675 55.8 55

e910 -27 R101= 122.62 L10.-.-.- E10 =4 1.799 47.5 52

e10.11=0 (lens elements stuck together) R111- 165.15 L11 E11 =4 1.531549.0 52

The invention is not of course limited lby details of the 4. A telephotolens as claimed in claim 1, wherein the embodiment which has just beendescribed, and such ninth, tenth and eleventh elements are menisci ofeach details can vary without departure from the scope of the of whichthe concave surface is disposed towards the invention. image-receivingsurface. l What we claim is: 1. A telephoto lens for use in conjunctionwith an References Cited image-receiving surface, consisting of two lensgroups UNIT D STA PATENT designated G1 and G2, of which the lens groupG2 is E TES S arranged to be the nearer one to said surface, the lens2,187,780 1/1940 Gehfke et al- 4 35o-216 groups G1 and G2 having six`and ve elements respec- 2,629,285 2/1953 Bakel' -1 35o-215 X tively, thesix elements of the group G1 being a con-y vergent group formed by,going 'towards the image- FOREIGN PATENTS receiving surface, a rstbiconvex convergent element, a 1,358,865 6/1954 France second biconcavedivergent element, a third biconvex convergent element, a fourthbiconcave divergent element, a fifth biconvex convergent element and asixth biconcave I OHN K, bCQRLBIN, Primary Examiner

